黄土高原东部(山西阳曲)1.2 Ma以来黄土记录的两次显著干旱化事件  

Two Significant Stages in the Aridification of the Eastern Chinese Loess Plateau since 1.2 Ma

作　　者：毛永栋 王治祥[2] 庞志斌[1] Mao Yongdong;Wang Zhixiang;Pang Zhibin(Shanxi Geological Survey Institute,Taiyuan 030000,China;School of Earth Sciences,China University of Geosciences,Wuhan 430074,China)

机构地区：[1]山西省地质调查院,山西太原030000 [2]中国地质大学地球科学学院,湖北武汉430074

出　　处：《地球科学》2021年第1期272-280,共9页Earth Science

基　　金：中国地质调查局地质调查工作项目(No.12120113059300);国家自然科学基金(No.41322013).

摘　　要：重建第四纪时期亚洲内陆干旱过程和沙漠的扩张历史对于我们了解东亚冬季风演变具有重要意义.然而目前对于黄土高原的干旱过程的研究主要聚焦于吕梁山以西的黄土地区,对于其东部还缺乏相应研究.为此,我们对吕梁山东部约1.2 Ma以来的阳曲黄土剖面进行了磁化率和元素含量测试,结果显示阳曲地区在1.2 Ma以来经历了两次明显的干旱事件.第一次干旱化事件发生在0.94 Ma,表现为Si、Fe百分含量和Rb/Sr比值显著减小而Ca含量明显增加,这次事件可能主要与大气CO2浓度下降导致全球冰量增加,特别是北半球冰盖扩张相关.第二次事件发生在0.31 Ma左右,Rb/Sr比值显著下降,Ca含量显著增高,这次事件可能是由于忻定古湖裂解引起区域干旱增强所致.Reconstruction of the progressive drying and expansion of deserts in eastern Asia during the Quaternary period is important for understanding the evolution of East Asian winter monsoon.The eolian deposits preserved in the Chinese Loess Plateau(CLP)are an unparalleled record of major wet/dry oscillations superimposed on the general drying trend of the Gobi and other nearby deserts of inland Asia.The element concentrations of these loess deposits in the Yangqu section in the eastern Loess Plateau indicate two major stages in the general aridification since 1.2 Ma.The first major step in aridification occurred at 0.94 Ma as indicated by an abrupt decrease of Si,Fe and Rb/Sr proportions and a significant increase of Ca content.We consider that the dominant factor for this drying step in eastern Loess Plateau was the increase of global ice volume,especially of Northern Hemisphere ice sheets,which force the Intertropical Convergence Zone to shift southward and inhibit the northward movement of moisture monsoon airflows.The second stage toward present aridification occurred at about 0.31 Ma.This step may be a localized regional event,perhaps attributed to the breach of Xin⁃Ding paleolake.

关 键 词：黄土高原 阳曲 元素变化 干旱化 古气候学 

分 类 号：P532[天文地球—古生物学与地层学]